Swinghacks——動感JList

ok，我承認動感這個詞用的有點過，還是先看效果

解釋一下，圖片中是沒有什麼動感的，其實效果是這樣

當選中item時，藍色的選中背景會從白色漸層到藍色，給人動感～

雖然這種動感沒有特別實際的用處，不過實現原理還是有點意思，來看看

1、先通過lookandfeel擷取選中和未選中的背景顏色，在轉換成rgb浮點數組float[3]

        UIDefaults uid = UIManager.getLookAndFeel().getDefaults();        Color listForeground =  uid.getColor ("List.foreground");        float[] foregroundComps = listForeground.getRGBColorComponents(null);

2、在valueChanged方法中，啟動thread做背景漸層效果；通過計時，每50ms進行一次repaint，總共執行500ms

        public void run() {            startTime = System.currentTimeMillis();            stopTime = startTime + ANIMATION_DURATION;            while (System.currentTimeMillis() < stopTime) {                colorizeSelections();                repaint();                //每間隔ANIMATION_REFRESH時間就repaint一次                try { Thread.sleep (ANIMATION_REFRESH); }                 catch (InterruptedException ie) {}            }            // one more, at 100% selected color            colorizeSelections();            repaint();        }

3、repaint之前調用colorizeSelections方法設定背景前景顏色，而colorizeSelections方法是根據時間來計算背景顯示的百分比

這個計算其實就是把背景的rgb值取百分比

        public void colorizeSelections() {            // calculate % completion relative to start/stop times            float elapsed = (float) (System.currentTimeMillis() - startTime);            float completeness = Math.min ((elapsed/ANIMATION_DURATION), 1.0f);            // System.out.println ("completeness = " + completeness);            // calculate scaled color            float colorizedForeComps[] = new float[3];            float colorizedBackComps[] = new float[3];            for (int i=0; i<3; i++) {                colorizedForeComps[i] =                    foregroundComps[i] +                    (completeness *                      (foregroundSelectionComps[i] - foregroundComps[i]));                colorizedBackComps[i] =                    backgroundComps[i] +                    (completeness *                      (backgroundSelectionComps[i] - backgroundComps[i]));            }

這樣repaint之前就設定好了背景色，不斷repaint的話就產生動感漸層的效果了

上代碼：

import java.awt.*;import javax.swing.*;import javax.swing.event.*;import java.util.*;public class AnimatedJList extends JList     implements ListSelectionListener {    static java.util.Random rand = new java.util.Random();    static Color listForeground, listBackground,        listSelectionForeground, listSelectionBackground;    static float[] foregroundComps, backgroundComps,        foregroundSelectionComps, backgroundSelectionComps;    static {        UIDefaults uid = UIManager.getLookAndFeel().getDefaults();        listForeground =  uid.getColor ("List.foreground");        listBackground =  uid.getColor ("List.background");        listSelectionForeground =  uid.getColor ("List.selectionForeground");        listSelectionBackground =  uid.getColor ("List.selectionBackground");        foregroundComps =            listForeground.getRGBColorComponents(null);        foregroundSelectionComps =             listSelectionForeground.getRGBColorComponents(null);        backgroundComps =            listBackground.getRGBColorComponents(null);        backgroundSelectionComps =            listSelectionBackground.getRGBColorComponents(null);    }    public Color colorizedSelectionForeground,        colorizedSelectionBackground;    public static final int ANIMATION_DURATION = 500;    public static final int ANIMATION_REFRESH = 50;    public AnimatedJList() {        super();        addListSelectionListener (this);        setCellRenderer (new AnimatedCellRenderer());    }    public void valueChanged (ListSelectionEvent lse) {        if (! lse.getValueIsAdjusting()) {            HashSet selections = new HashSet();            // System.out.println ("got last lse");            for (int i=0; i < getModel().getSize(); i++) {                if (getSelectionModel().isSelectedIndex(i))                    selections.add (new Integer(i));            }            CellAnimator animator = new CellAnimator (selections.toArray());            animator.start();        }    }    public static void main (String[] args) {        JList list = new AnimatedJList ();        DefaultListModel defModel = new DefaultListModel();        list.setModel (defModel);        String[] listItems = {            "Chris", "Joshua", "Daniel", "Michael",            "Don", "Kimi", "Kelly", "Keagan"        };        Iterator it = Arrays.asList(listItems).iterator();        while (it.hasNext())            defModel.addElement (it.next());        // show list        JScrollPane scroller =            new JScrollPane (list,                            ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,                            ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);        JFrame frame = new JFrame ("Checkbox JList");        frame.getContentPane().add (scroller);        frame.pack();        frame.setVisible(true);    }    class CellAnimator extends Thread {        Object[] selections;        long startTime;        long stopTime;        public CellAnimator (Object[] s) {            selections = s;        }        public void run() {            startTime = System.currentTimeMillis();            stopTime = startTime + ANIMATION_DURATION;            while (System.currentTimeMillis() < stopTime) {                colorizeSelections();                repaint();                try { Thread.sleep (ANIMATION_REFRESH); }                 catch (InterruptedException ie) {}            }            // one more, at 100% selected color            colorizeSelections();            repaint();        }        public void colorizeSelections() {            // calculate % completion relative to start/stop times            float elapsed = (float) (System.currentTimeMillis() - startTime);            float completeness = Math.min ((elapsed/ANIMATION_DURATION), 1.0f);            // System.out.println ("completeness = " + completeness);            // calculate scaled color            float colorizedForeComps[] = new float[3];            float colorizedBackComps[] = new float[3];            for (int i=0; i<3; i++) {                colorizedForeComps[i] =                    foregroundComps[i] +                    (completeness *                      (foregroundSelectionComps[i] - foregroundComps[i]));                colorizedBackComps[i] =                    backgroundComps[i] +                    (completeness *                      (backgroundSelectionComps[i] - backgroundComps[i]));            }            colorizedSelectionForeground =                new Color (colorizedForeComps[0],                           colorizedForeComps[1],                           colorizedForeComps[2]);            colorizedSelectionBackground =                new Color (colorizedBackComps[0],                           colorizedBackComps[1],                           colorizedBackComps[2]);            // System.out.println ("fore = " +colorizedSelectionForeground);            // System.out.println ("back = " +colorizedSelectionBackground);        }    }    class AnimatedCellRenderer extends DefaultListCellRenderer {        public Component getListCellRendererComponent(JList list,                                                      Object value,                                                      int index,                                                      boolean isSelected,                                                      boolean hasFocus) {            Component returnMe =                super.getListCellRendererComponent (list, value, index,                                                    isSelected, hasFocus);            if (isSelected) {                returnMe.setForeground (colorizedSelectionForeground);                returnMe.setBackground (colorizedSelectionBackground);                /* this might be necessary if you have more                   elaborate cells                if (returnMe instanceof Container) {                    Component[] children =                        ((Container)returnMe).getComponents ();                    System.out.println (children.length + " children");                    for (int i=0;                         (children != null ) && (i<children.length);                         i++) {                        children[i].setForeground (colorizedSelectionForeground);                    children[i].setBackground (colorizedSelectionBackground);                    }                }                */                if (returnMe instanceof JComponent)                    ((JComponent) returnMe).setOpaque(true);            }            return returnMe;        }    }}